基于Java protected的深入理解

//代码1：包A中有一个动物类 
package testa; 
public class Animal { 
    protected void crowl(String c){ 
        System.out.println(c); 
    } 
} 
//代码2：包B中有两个类――猫类和鼠类 
package testb; 
import testa.Animal; 
class Cat extends Animal{ 

} 
class Rat extends Animal{ 
    public void crowl(){ 
                crowl("zhi zhi"); //没有问题，继承了Animal中的protected方法――crowl(String) 
            Cat cat=new Cat(); 
                cat.crowl("miao miao"); //wrong, The method crowl(String) from the type Animal is not visible 
    } 
}